The present disclosure is directed to a device comprising a control unit and a plurality of resistive cells, in particular a resistive memory device comprising a plurality of resistive memory cells. The disclosure further concerns a related method and a related computer program product.
One example for resistive memory devices is phase-change memory (PCM) devices. PCM is a non-volatile solid-state memory technology that exploits the reversible, thermally-assisted switching of phase-change materials, in particular chalcogenide compounds such as GST (Germanium-Antimony-Tellurium), between states with different electrical resistance. The fundamental storage unit (the “cell”) can be programmed into a number of different states, or levels, which exhibit different resistance characteristics. The s programmable cell-states can be used to represent different data values, permitting storage of information.
Reading and writing of data in PCM cells is achieved by applying appropriate voltages to the phase-change material via a pair of electrodes associated with each cell. In a write operation, the resulting programming signal causes Joule heating of the phase-change material to an appropriate temperature to induce the desired cell-state on cooling. Reading of PCM cells is performed using cell resistance as a metric for cell-state. An applied read voltage causes current to flow through the cell, this current being dependent on the resistance of the cell. Measurement of the cell current therefore provides an indication of the programmed cell state. A sufficiently low read voltage is used for this resistance metric to ensure that application of the read voltage does not disturb the programmed cell state. Cell state detection can then be performed by comparing the resistance metric with predefined reference levels for the s programmable cell-states.
One of the major problems with the existing Phase Change Memory is that the material that is currently used in the memory cell of a PCM changes its phase from a high resistance amorphous to a low resistance crystalline state. Although the crystalline state is stable in time, the amorphous state is continually evolving thereby making the resistance of the high resistance state to not stay well defined, but to evolve/drift in time. Accordingly, there is a need for other memory devices.